Being non-heterosexual is just plain harder than being heterosexual. Besides the fact that a lot of people will look down upon you for your non-standard relationships and sexual practices, you're pulling from a much smaller dating pool. It's just harder.
So much so, that you almost have to believe that people are born as or unable to help or control their non-heterosexual orientation. Because nobody would choose that kind of difficulty in life, just for fun.
However, if we go down that road, believing that a non-standard sexual orientation -- meaning someone can't reproduce in the conventional way -- is an inborn, immutable trait, then we're also buying into the idea that non-heterosexuality is essentially a handicap. Their sexuality is in a wheelchair. Other people can reproduce and get turned on by sexual acts that cause reproduction. They can't. They're handicapped.
Essentially, this post is saying that picking on non-heterosexuals is like beating up the kid in the wheelchair, so don't do it.